This photograph was mentioned during one of my presentations at Megalithomania 2018, in Glastonbury.
It is one of about seven photographs I took of a Holy well during a survey trip to Anglesey on 15th May 2011. I filed these and did not pick up on this particular photograph until 2016. Only one had this anomalous light, which appears to be a double or triple light source that is leaving a diaphanous trail as it rises from the water source.
Make of it what you will, the photo shown here is exactly what emerged from the memory card in the digital camera, a Nikon 4300.